Railway signaling apparatus



Get. 8, 1946. JEROME A 2,409,044

RAILWAY'SIGNALIN? APPARATUS Filed Jan. 9, 1943 9 Sheets- Sheet 1 IN VENTOR Amizurll .Japome.

1115 ATTORNEY A. 1.. JEROME RAILWAY SIGNALING APPARATUS Filed Jan. 9,1943 9 Sheets-Sheet 2 6 W5 B I m 5 x A72 2 L M Cen12 on g *7 46JCL- 215' v 19 M F4 4 2' I) 22 5) Y /66 zaj w 67 Li] 2 L] a $67M A6T\ Z1 B6T-ii V Fm] up 157' [MUD] v v INVENTOR AmizurlhJepome. "aim 15 ATTORNEYOct. 8, 1946.

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Filed Jan. 9, 1943 9 Sheets-Sheet 9- QQQQQ! A.

N .L Q N k is; B Q N i 2; E s b a a? \I INVENTOR i -Arzl2aPL.JePome. fr4 av-am N H15 ATTORNEY Patented Oct. 8, 1946 RAILWAY SIGNALINGAPPARATUS Arthur L. Jerome, Edgewood, Pa., assignor to The Union Switch& Signal Company,

Swissvale,

Pa., a corporation of Pennsylvania Application January 9, 1943, SerialNo. 471,838

17 Claims.

My invention relates to railway signaling apparatus and particularly toimproved means for indicating occupancy of a portion of a track stretchwhich may not coincide with the track sections into which the trackstretch is divided for the control of trafilc through the track stretch.

It is customary to divide the track rails of a track stretch into tracksections by insulated joints, and to equip each of these track sectionswith track circuit apparatus for the control of signaling apparatugoverning movement of traffic through the track stretch.

In some situations, as for example the control of highway crossingsignals or the lockin of switches, it is desirable to determineoccupancy of a portion of the track stretch which does not coincide withthe track sections which are established for the control of the trafficgoverning signal equipment. In order to secure the desired control insuch situations it has been customary heretofore to divide the tracksections into subsections and to equip each of these subsections withtrack circuit apparatus, while when more than one track section isinvolved a line circuit controlled by the track relays is pro- Vided.

The additional track circuit and other equipment for the subsections isrelatively expensive, and if a track stretch includes many highwaycrossings or track witches so that numerous subsections are required,the cost of the equipment may be excessive.

It is an object of this invention to provide im-- proved train detectingapparatus which may be applied to a stretch of railway track toascertain occupancy of a portion of aid track stretch withoutinterfering with the operation of the track circuit apparatus with whichthe track sections are provided to control tramc in the track stretch.

Another object of the invention is to provide improved train detectingapparatu which makes it unnecessary to subdivide the track sections of atrack stretch when the portion of the stretch in which it is desired todetermine occupancy does not coincide with the track sectionsestablished to control the traffic governing signals.

A further object of the invention is to provide improved auxiliary trackcircuit apparatus of the type described which may be arranged so thatits failure will not interfere with the operation of the principal trackcircuit apparatus.

Another object of the invention is to provide auxiliary track circuitapparatus of the type described which may be controlled by the principaltrack circuit apparatus so that the auxiliary track circuit apparatus isnormally deenergized and is energized only when the principal trackcircuit apparatus detects a train in the portion of the track stretch inthe vicinity of the auxiliary track circuit apparatus.

A further object of .the invention is to provide improved auxiliarytrack circuit apparatus of the type described which is arranged so thata first set of such apparatus may be employed to detect occupancy of a.first portion of a track stretch, and so that a second set of suchapparatus may be employed to detect occupancy of a second portion of thetrack stretch even though the two portions of the track stretch overlapso that some of the track stretch is common to both portions.

Another object of the invention i to provide improved auxiliaryv trackcircuit apparatus of the type described which is adapted to detectoccupancy of a zone in a track stretch even though this zone extendsbeyond the confines of a track section.

A further object of the invention is to provide improved auxiliary trackcircuit apparatus of the type described which employs an electron tubegoverned by occupancy of a selected zone in a track stretch, theapparatus being arranged so that failure of the electron tube cannotcreate a hazardous condition.

Another object of the invention is to provide improved highway crossingsignal control means employing the auxiliary track circuit apparatusprovided by this invention.

A further object of the invention is to provide improved crossing signalcontrol means which is arranged so that the crossing signals arecontrolled jointly by the principal and the auxiliary track circuitapparatus, and so that failure of the auxiliary track circuit apparatuswill not result in failure of the crossing signals to provide adequatewarning of the approach of a train.

Other objects of the invention and feature of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawings. 7

I shall describe several forms of apparatus embodying my invention,together with several modifications thereof which I may employ, andshall then point out the novel features thereof in claims.

In practicing my invention, at each end of the track zone occupancy ofwhich is to be determined I connect a transformer with the section failsin such mamier as not to substantially interfere with the operation ofthe principal track circuit apparatus, while permitting energy to besupplied from one transformer to the other only when the interveningtrack zone is unoccupied. I supply alternating current of a distinctivefrequency to the track rails through one of these transformers and Iemploy energy from the other transformer to vary the potential on thegrid or control element of a cold cathode type electron tube, while Isupply alternating current to the anode circuit of this type in serieswith the winding of a control relay. The tube operates to permit halfcycles of energy of one polarity only to be supplied therethrough, andthen only when energy is supplied over the associated track zone toestablish the proper potential on the tube grid or control element.

In the drawings Fig. 1 is a diagram showing a stretch of railway trackequipped with highway crossing signal control apparatus embodying myinvention,

Figs. 2, 3, 4., 4A, 5, 6, 7, 8, 9, 9A, and. 10 illustrate modificationswhich may be employed,

Fig. 11 is a diagram showing a stretch of railway track in which thecrossing signals for two highway intersections are governed by apparatusembodying this invention,

Figs. 12 and 13 are diagrams showing crossing signal control meansembodying this invention applied to track sections in which codedalternating current track circuit energy is employed, and

Fig. 14 is a diagram showing switch locking means embodying thisinvention.

Similar reference characters refer to similar parts in each of theseveral views.

Referring to Fig. 1 of the drawings, there is shown therein a stretch ofrailway track over which trafiic normally moves in the directionindicated by the arrow, that is from left to right. The rails l and 2 ofthe track stretch are divided by insulated joints 3 into track sectionsfor signaling purposes. One such section is shown in Fig. l and isdesignated 5T.

The track section 5T has at the entrance end thereof a wayside signal 58which may be of any appropriate type and is controlled in accordancewith traffic conditions in section ST and in the adjacent section inadvance. As shown the signal 58 is of the familiar color light type andhas a green or proceed lamp G, a yellow or caution lamp Y, and and orstop lamp R.

As shown the track section ST is provided with coded track circuitapparatus of well known design. The track circuit apparatus includes acoding relay 5CTM at the exit end of the section and having a contact H)which controls connection of the track battery 5TB across the sectionrails. The relay ECTM is controlled by traffic conditions in section GTin the manner well known in the art so that contact I of relay CTM isoperated between its released and picked-up periods so as to causeenergy of 75 or 180 code frequency to be supplied to the rails ofsection .BT according as section GT is occupied or is unoccupied.

A code following track relay 5TB is connected across the section railsat the entrance end of the section and has associated therewith adecoding transformer 5DT, and auxiliary relays 5H and SJ. When the tracksection is vacant relay 5TB follows code and its contact l2 alternatelyestablishes the circuits of the two portions of the decoding transformerprimary winding so that energy is induced in the transformer secondarywindings. The energy from one of the transformer secondary windings isrectified and supplied to code detecting relay 5H so that the contactsof relay 5H are picked up as long as relay 5TB, follows code of either'75 or 180 code frequency.

The energy from the other secondary winding of the decoding transformeris supplied through a resonant rectifier unit IBUDU to relay 5J. Theelements of the unit IDU are proportioned so that sufficient energy topick up relay 5J is supplied through the unit when and only when therelay 5TB is responding to energy of 180 code frequency.

The relays 5H and EJ cooperate in the usual manner to control signal 58so that this signal displays its red or stop indication when relay 5H isreleased, and when relay 5H is picked up the signal 58 displays itscaution or its proceed indication according as relay 5J is released orpicked up.

The relay 5H also controls the supply of energy to coding relay lCTM sothat this relay is energized over a circuit controlled by a contact of acode transmitter T or of a code transmitter lBflCT depending on whetherrelay 5H is released or picked up.

The track section 5T includes an intersection with a highway H and thisinvention is directed to auxiliary track circuit means for controllingthe crossing signals XS at the intersection to warn users of the highwayof the approach of a train.

An insulated joint I5 is placed in one of the track rails at a point onthe right-hand side of the intersection, while the portions of the trackrail on opposite sides of the insulated joint are connected togetherthrough a reactor IS. The reactor I6 is designed so that it hasrelatively little impedance to the coded direct current traificgoverning energy, but has high impedance to alternating current employedin the control of the crossing signals.

A transformer T has a secondary winding having its center terminalconnected to track rail I, while one end terminal of this winding isconnected through a resistance I8 to the portion of rail 2 on one sideof the joint [5, and the other end terminal of the transformer secondarywinding is connected through resistance l9 to the portion of track rail2 on the other side of the insulated joint i5. Accordingly, when energyis supplied to the primary winding of transformer T, one half of thetransformer secondary winding supplies alternating current to theportion of the track section on one side of the joint l5, and the otherhalf of the transformer secondary winding supplies current to theportion of the track section on the opposite side of the joint l5, whilethe reactor It prevents flow of alternating current energy between theportions of rail 2 on opposite sides of the joint l5 and thus preventsshort circuiting of the transformer secondary winding.

The resistances l8 and i9 have relatively high resistance to therebyreduce to a very small value the now of coded direct current trackcircuit energy between the track rails through the two portions of thetransformer secondary winding.

An insulated joint 2:] is located in rail 2 at the point in the rear ofthe intersection at which it is desired to have operation of thecrossing signals initiated by a train moving in the normal direction oftrafiic, while a similar insulated joint 22 is located in rail 2 at thepoint in advance of the intersection at which it is desired 5 to haveoperation of the crossing signals initiated by a train moving in thereverse of the normal direction.

A grid transformer AGT has the terminals of its primary windingconnected to the rail 2 on opposite sides of the insulated joint 20,while a grid transformer BGT has the terminals of its primary windingconnected to rail 2 on opposite sides of the joint 22. The transformersAGT and BGT are of such design that their primary windings have littleresistance to flow of coded direct current track circuit energy throughtrack rail 2.

The transformers AGT and BGT control electron tubes AT and BTrespectively, which in turn control relays ATR, and BTR, which governcircuits for supplying energy to slow release relays E and W, while therelays E and W control the circuits of the windings of the interlockingrelay XR which controls the crossing signals XS.

The electron tubes AT and BT are preferably of the cold cathode,controlled ionization type, while the associated relay together with asource of alternating current are connected across the anode and cathodeof the tube to energize the relay by current passed by the tube when thetube is ionized, the voltage of the source of alternating current being,however, normally insufficient to start ionization, but being sumcientto cause the tube to break down when a preselected control electromotiveforce is applied to the control element or grid of the tube.

Each tube is provided with a grid or control element which is governedby the associated grid transformer. As shown one terminal of thesecondary winding of the transformer AGT is connected through aresistance 40 and a condenser Iii to the grid 42 of the tube AT, Whilethe other terminal of the secondary winding of the transformer AGT isconnected to an intermediate point on a biasing resistor M which isconnected across the terminals of the secondary winding of transformerATT.

Similarly, one terminal of the secondary winding of grid transformer BGTis connected through a resistor (55 and a condenser 46 to the grid 48 oftube BT, while the other terminal of the transformer secondary windingis connected to an intermediate point on a biasing resistor 50 which isconnected across the terminals of the second ary winding of transformerBTT.

Alternating current is supplied from a transformer ST to the transformerT, and to transformers ATT and BTT associated with the electron tubes,while the supply of energy to transformer ST is governed by a controlrelay GB. The alternating current may be supplied from any suitablesource, not shown, the terminals of which are designated BX and CX.

The signal lamps and the relays other than the track relay are operatedby direct current supplied from a suitable source, such as storagebatteries, not shown, the terminals of which are designated B and C.

The equipment is shown in the condition which it assumes when sectionsET and GT are vacant. At this time energy of 180 code frequency issupplied to relay ECTM and it operates to supply energy of 180 codefrequency to the rails of section ET. This energy feeds over the sectionrails and through the reactor is and the primary windings oftransformers AGT and BGT to the track relay 5TB, and operates it so thatenergy is supplied through the decoding transformer to relays 5H and 5J.As relays 5H and EU are both picked up the green or clear lamp G ofsignal 53 is lightedwhile as relay 51-1 is picked up its contact 25establishes the circuit to supply energy of 180 code frequency to relay4CTM so that energy of 180 code frequency is supplied to th rails ofsection 4T.

As relay 5H is picked up its contact 26 establishes the circuit ofcontrol relay CR and it is picked up so that its contact 21 establishesa circuit for relay W, while its contact 28 establishes a circuit forrelay E. Accordingly, relays 'E and W are both energized and theyestablish the circuits of the windings 3e and 31 of relay XR. so thatcontacts 32 and as of the interlocking relay are both picked up, andinterrupt the supply of energy to the crossing signals XS and thusprevent operation of the crossing signals.

As relay CR is picked up its contact 35 interrupts the supply of energyto transformer ST, and thus cuts off the supply of alternating currentto the track rails and t the electron tubes; Accordingly the electrontubes and other portions of the auxiliary track circuit apparatus do notfunction when the track section is vacant, while the crossing signalsare controlled by the usual track circuit apparatus as long as thesection is vacant.

When a train moving in the normal direction of traffic enters section ETthe track relay TB ceases to follow code and relays 5H and tJ releaseand cause the signal 58 to display its red or stop indication and changethe energy supplied to relay iCTM from 180 to '75 code frequency.

On release of relay 5H its contact 26 interrupts the circuit of relay CRand relay CR releases so that its contact 35 establishes the circuit ofthe primary winding of transformer ST and energy is supplied from thistranformer to the primary windings of transformers ATT, BTT and T.

On the supply of energy to transformer T energy is supplied from onehalf of the transformer secondary winding through resistor i8 tot-heportion of the track section in the rearof the 45 intersection. Thisenergy feeds from an end terminal of the transformer secondary windingthrough resistor iii, rail 2, primary winding of transformer AGT,through the wheels and axles of the vehicles forming the train, ando-verraii so I to the center terminal of the transformer primarywinding.

Similarly, energy is supplied from the other half of the secondarywinding of transformer T to the portion of the track section in advanceof 55 the intersection. This energy feeds from the end terminal of thetransformer through resistor l9, track rail 2, primary winding oftransformer BGT, thence over back contact of relay SCTM or through thebattery 5TB and front contact iii of relay 5CTM, and rail i to thecenter terminal of the transformer secondary winding.

In addition on the supply of energy to transformer ST energy is suppliedtherefrom to transformers ATT and BT'I' with the result that en- 65 ergyis induced in the secondary winding of each of these transformers and isimpressed between the anode and cathode of the associated tube,

while a portion of the transformer secondary voltage is impressed on thegrid of the associated 70 tube through the biasing resistor.

As pointed out above, the voltage of the energy impressed'between theanode and cathode of each tube is insufficient to cause ionization ofthe tube. The potential applied to the grid of each tubeby 75 energysupplied thereto through the biasingresistor is insufficient to causeionization of the tube, so that unless energy is supplied to the tubegrid from the associated grid transformer the tube is not ionized and nocurrent flows in the tube anode circuit.

On the supply of alternating current through the primary winding of gridtransformer AGT energy of relatively high voltage low amperage isinduced in the transformer secondary winding and is supplied therefromto the grid 42 of the tube AT.

During the half cycles in which the energy supplied from the gridtransformer AGT to the grid 42 of the tube AT are of positive relativepolarity the potential on the tube grid is increased to a valueeffective to ionize the tube and cause it to become conducting.

The transformers AGT and ATT are supplied from the same source so theenergy impulses supplied from these transformers to the tube AT aresubstantially in phase. The various parts of the equipment are arrangedso that when an impulse of energy of positive polarity is supplied fromgrid transformer AGT to the grid of tube AT, the impulse of energysupplied from the transformer ATT is of such polarity that the positiveterminal of the transformer secondary winding is connected to the anodeof the tube AT. The tube AT, therefore, breaks down and en rgy flowsthrough the tube to relay ATR over the circuit which is traced from anend terminal of the secondary winding of transformer ATT to the tubeanode 5|, through the tube space to cathode 52, and Winding of relay ATRto the other terminal of the transformer secondary winding.

The tube AT, once it has become conducting, continues to be conductingthroughout most of the positive half cycle of energy from thetransformer ATT. The next or negative half cycle of energy from thetransformer ATT serves to deenergize the tube and restore it to itsnormal condition, while as long as energy continues to be supplied fromthe grid transformer to the tube grid, the tube is rendered conductingon each subsequent positive half cycle so that an impulse of energy issupplied to the winding of relay ATR during every other half cycle ofthe alternating current.

A condenser 55 is preferably connected across the terminals of thewinding of relay AIR, and during the supply of each impulse of energythrough the tube AT, a charge is built up on the condenser 55, while inthe intervals between impulses of energy from the tube, energy from thecondenser feeds to the relay winding and maintains the flow of energythrough the relay winding and thus maintains the relay contacts pickedup. If desired the relays ATR and BTR may be of a type the contacts ofwhich are slow to release so that they will remain picked up in theintervals between the energy impulse-s supplied to the relay winding,and thus eliminate the need for condensers connected across theirterminals.

On the supply of alternating current to the primary winding oftransformer BGT the tube ET is rendered conducting and energy fromtransformer B'I'I is supplied through the tube to relay IB'IR to pick upits contact.

On picking up of relay ATR its contact 56 establishes a circuit tosupply energy to a winding of relay E, while on picking up relay BTR itscontact 58 establishes a circuit to supply energy to relay W.

There is a short period between the time at which relay CR releases andinterrupts the circuits which it controls for supplying energy to relaysE and W, and the time at which relays A'IR and BTR pick up and establishcircuits for the relays E and W. The relays E and W are of a type whichare slow in releasing so their contacts remain picked up throughout thisperiod and maintain the circuits of the windings of the interlockingrelay XR.

Accordingly, when a train enters section 5T relay CR releases andinterrupts the circuits which it controls for supplying energy to therelays E and W, while the auxiliary track circuit apparatus provided bythis invention is placed in operation and causes the relays ATR and BTRto be picked up and establish circuits to supply energy to the relays Eand W so that they continue to prevent operation of the crossingsignals.

When the train advances beyond the joint 20, the wheels and axles of thevehicles forming the train provide a path between the rails I and 2which shunts the alternating current away from transformer AGT, andenergy is no longer supplied to the transformer AGT while energy is nolonger supplied from the transformer AGT to the grid of tube AT.Accordingly, the tube AT ceases to be conducting so energy ceases to besupplied to relay ATR and its contact 55 releases and interrupts thesupply of energy to relay E. Contact 65 of relay E therefore releasesand interrupts the circuit of the winding 30 of relay XR so that thecontact 32 controlled by winding 30 releases and establishes the circuitof the crossing signals XS and these operate to yarn users of thehighway of the approach of a train.

When the train advances beyond the joint IS the supply of energy totransformer BGT is cut off and the tube ET is rendered non-conducting sorelay BTR releases and interrupts the circuit of relay W with the resultthat contact 6| of relay W interrupts the circuit of winding 3| of theinterlocking relay XR. The internal construction of the relay XR is suchthat on deenergization of winding 3| while winding 35 is deenergized thecontact 33 is prevented from moving all of the way to its releasedposition.

When the rear of the train vacates the portion of the track section inthe rear of the joint t5 alternating current is again supplied throughthe primary winding of transformer AGT so energy is supplied from thetransformer secondary winding to the grid 42 of tube AT so that the tubeis rendered conducting and energy is supplied to relay ATR to pick upits contact 55.

The alternating current energy supplied to transformer AGT at this timeis supplied through the winding of relay 5TH. The value of thisalternating current energy is too small to cause operation of the relay,however.

On picking up of contact 55 of relay ATR energy is supplied to relay Eand its contact 6!] establishes the circuit of the winding 30 of re- 1ayXR so that contact 32 is picked up and discontinues operation of thecrossing signals XS, which is proper as the rear of the train hascleared the highway intersection.

The internal construction of the interlocking relay XR is such that onpicking up of contact 32 contact 33 is prevented from moving to itsreleased position to establish the circuit of the crossing signals.

When the rear of the train advances beyond the joint IS the shuntingeffect of the train on the alternating current supplied to the portionof the track section in the rear of the joint I is relatively smallbecause of the impedance of the reactor to the alternating current.Accordingly, as soon as the rear of the train passes over the joint 55there is a substantial increase in the alternating current supplied totransformer AGT and the tube AT is rendered conducting so relay ATR willbecome picked up to discontinue operation of the crossing signals. Thereactor l6, therefore, serves to insure that operation of the crossingsignals will be discontinued as soon as the train clears theintersection.

When the rear of the train advances beyond the joint 22, alternatingcurrent is again supplied through the primary winding of transformer BGTso that the tube ET is again rendered conducting. Accordingly, relay BTRpicks up and establishes a circuit for relay W and contact Si of relay Wpicks up and establishes the circuit of winding 3! of the interlockingrelay XR so that contact 33 of relay 2B is picked up.

W hen the train advances far enough to vacate section ET the impulses ofcoded direct current supplied from the track battery 5TB to the trackrails during the picked-up periods of contact Iii of coding relay ECTMfeed through the primary windings of transformers .BGT and AGT andthrough the reactor it to the track relay 5TB and operate it so thatenergy is supplied through the decoding transformer EDT to relay 5H. Atthis time energy of '75 code frequency is supplied to section ET and therate of operation of relay 5TB is such that too little energy issupplied to relay 5J through the associated resonant unit to pick up therelay contacts. Accordingly, relay 5J remains released and on picking upof relay 5H energy is supplied to the yellow lamp Y of signal 58 over afront contact of relay 5H and a back contact of relay SJ, while onpicking up of relay 5H its contact changes the energy supplied tosection lT from '75 to 180 code frequency.

In addition, on picking up of relay 5H its contact 26 establishes thecircuit of relay CR so that its contacts 2? and 28 establish circuits tosup-- ply energy to relays W and E, while its contact 35 interrupts thesupply of energy to transformer ST and thus cuts oil the supply ofalternating current energy to the track rails, and also cuts off thesupply of energy to the transformers ATT and BTT associated with thetubes AT and BT. Accordingly, energy is no longer supplied through thetubes to relays ATR and BTR and they release and interrupt the circuitswhich they control for supplying energy to the relays E and W. Beforethis occurs, however, energy is supplied to relays E and W over thecircuits established by relay CR so the relays E and W remain picked upand maintain the circuits of the windings 39 and 3| of interlockingrelay XR and thus prevent operation of the crossing signals at thistime.

This system also operates to provide proper control of the crossingsignals on movement of a train through the track stretch in the reverseof the normal direction.

When a train moving the reverse direction enters section 51 it shuntsthe track rails so as to prevent the supply of coded. direct current tothe track relay it'remains released so that relay 5H releases. Onrelease of relay 5H its contact 25 interrupts the circuit of relay CR sothat it releases and interrupts the circuits which it controls forsupp-lying energy to relays E and W. In addition, on release of relay CRits contact 35 establishes the circuit for supplying energy to thetransformer ST so that energy from this transformer is supplied to thetransformers ATT and BTT associated with tubes AT and BT, and is alsosup-plied through transformer T and over the section rails to the gridtransformers AGT and BGT to render the tubes conducting. Accordinglyenergy is supplied through the tubes to pick up relays ATR and BTR andthey establish circuits for relays E and W and thus prevent operation ofthe crossing signals XS.

When the train advances beyond the joint 22 transformer BGT is shuntedand tube ET is rendared non-conducting so that relay BTR releases andinterrupts the circuit of relay W. Contact 6i of relay W, therefore,releases and interrupts the circuit of winding 3| of relay XR andcontact 33 of relay XR releases and establishes the circuit of thecrossing signals XS so that they operate towarn users of the highway ofthe approach of a train.

When the train advances beyond the joint 15 it shunts the transformerAGT so that tube AT is rendered non-conducting and relay ATR releasesand causes release of relay E with resultant interruption of the circuitof the winding 30 of relay KB. The internal construction of relay XR issuch, however, that contact 32 is prevented from moving to its releasedposition at this time.

When the train vacates the portion of the track section betweeninsulated joints l5 and 22 energy is again supplied to transformer BGTso that tube ET is rendered conducting and relay BTR is picked up andestablishes the circuit of relay W. Accordingly contact 6| of relay Wpicks up and establishes the circuit of the winding 3! of relay XE sothat contact 33 is picked up and discontinues operation of the crossingsignals XS.

When the train vacates the portion of the track section betweeninsulated joints l5 and 20 energy'is again supplied to transformer AGTso that tube AT is rendered conducting and energy is supplied to relayATR to pick up its contact and establish the circuit of relay E with theresult that contact Bil of relay E establishes the circuit of thewinding 36 of relay XR.

When the train vacates section ET, the impulses of coded direct currentsupplied to the section rails feed to relay 5TB and operate it so thatrelay EH is picked up to establish the circuit of relay CR. and it picksup to establish circuits for the relays E and W and to discontinueoperation of the auxiliary track circuit apparatus.

When the front of a train moving in the normal direction, or the rear ofa train moving in the reverse direction, is at a point in the tracksection intermediate the insulated joints l5 and 22, alternating currentfrom transformer T is prevented from reaching transformer BGT, but codeddirect current supplied at the exit end of the section flows through theprimary winding of transformer EST and may cause impulses of energy tobe induced in the secondary winding of the transformer and thereforecause impulses to be supplied to the grid of the tube ET. Thetransformer BGT and the other portions of the apparatus are proportionedso that the impulses of energy supplied to the tube grid as a result ofthe flow of the impulses of coded direct current through the primarywinding of transformer BC-T are of such value as to be ineffective torender the tube conducting. Accordingly the relay BTR is released underthe conditions outlined.

Th relay BTR may be of a type the contacts of which are slow to pick up,while the condenser 64 connected across the terminals of the relaywinding renders the relay slow to pick up. The relay BTR and theassociated condenser may be proportioned so that the relay will not pickup if supplied with impulses of energy at the frequency of the codedtrack circuit energy if the impulses of coded track circuit energysupplied through the transformer BGT should cause the tube BT to becomeconducting.

The coded track circuit current is of relatively low frequency, thehighest code speed usually employed being 180 cycles a minute, or 3cycles a second. The alternating current employed in the track circuitis of much higher frequency, such as 60 or 100 cycles a second, so therewill be a great difierence between the frequency of the supply ofimpulses of energy to relay BTR when the tube ET is rendered conductingby alternating current supplied to the transformer BGT and when the tubeis rendered conducting by coded track circuit energy supplied throughthe transformer BGT. Accordingly, the relay BTR and the associatedapparatus may be proportioned so that the relay will pick up whenalternating current is supplied to transformer BGi'I, but to not pick upwhen coded track circuit energy is supplied to transformer BGT.

It will be seen that this crossing signal control system operates sothat the traific governing track circuit apparatus operates to preventoperation of the crossing signals as long as the track section isvacant, while the auxiliary track circuit apparatus is deenergized aslong as the section is vacant. As soon as the track section is occupiedthe auxiliary track circuit apparatus is energized and control of thecrossing signals is transferred to the auxiliary track circuitapparatus, while the auxiliary track circuit apparatus serves to preventoperation of the crossing signals until the train advances to within aselected distance from the crossing.

When a train moving in either direction enters an approach section forthe crossing, the crossing signals are placed in operation, while theauxiliary track circuit apparatus operates to discontinue operation ofthe crossing signals as soon as the approach section is vacated. Thecrossing signals remain under the control of the auxiliary track circuitapparatus as long as the section is occupied, but as soon as the sectionis vacated the traffic governing track circuit apparatus assumes controlof the crossing signals and discontinues operation of the auxiliarytrack circuit apparatus.

Since the auxiliary track circuit apparatus is normally deenergized andbecomes energized only when the section is occupied, the wear on theelectron tubes is reduced to a minimum and their life is correspondinglyincreased, whil the energy consumed by the auxiliary track circuitapparatus is reduced to a minimum.

This system is arranged so that failure of the electron tubes or otherportions of th auxiliary track circuit apparatus will not produce anobjectionable failure of the crossing signals nor interfere with theproper functioning of the traific governing signal apparatus.

If when a train moving in the normal direction of trafiic enters thsection the tube AT is defective and will not function, relay ATR willremain released and will not establish a circuit for relay E, and thisrelay will release and interrupt the circuit of the winding 30 of relayXR so that contact 32 releases and establishes the circuit of thecrossing signals. Accordingly, operation of the crossing signals will beinitiated as soon as the 12 train enters section 5T instead of beingdelayed until the train advances beyond the insulated joint 20.

In addition when the tube AT is defective, operation of the crossingsignals will not be discontinued when the train passes the joint l5.Instead the signals will continue to operate until the train vacates thetrack section. When this occurs the trafiic governing track circuitapparatus functions in the normal manner and discontinues operation ofthe crossing signals and of the auxiliary track circuit apparatus.

Similarly, if the tube ET is defective operation of the crossing signalswill be initiated as soon as the section is occupied and will becontinued until the section is vacated.

If the tube failure is caused by short circuiting of the elements of thetube, th tube will cease to serve as a rectifier and alternating currentwill be supplied through the tube. The relay energized by currentsupplied through the tube is of the direct current type and its contactswill remain released on the supply of alternating current to the relaywinding.

Failure of the tubes, therefore, will cause operation of the crossingsignals to be initiated sooner and to be continued longer than usual.While this additional time of operation of the crossing signals maydelay users of the highway, it will not create a hazardous condition,and the operation of the equipment is such that users of the highway arealways provided with a warning of the approach of a train for at leastthe normal period.

In like manner failure of the line circuits connecting transformers ATIand BTT with the transformer T, or of the line circuits over which therelays ATR and BTR control the relays E and W, will result in prolongedoperation of the crossing signals but will not cause a failure of thecrossing signals to operate, and will not interfere with operation ofthe traffic governing signal apparatus. Failure of the line circuit overwhich relay 5H controls the relay CR, will result in continued operationof the auxiliary track circuit apparatus to control the crossingsignals, while operation of the crossing signals will be started andstopped at the usual times, and operation of the'traflic governingsignals will not be affected.

The auxiliary track circuit apparatus is shown controlled by the trafficgoverning signal apparatus so as to be deenergized when the associatedtrack section is vacant, and to be energized and control the crossingsignals only when the section is occupied. This is the preferredarrangement, but it is contemplated that the relay CR may be omitted andthe auxiliary track circuit apparatus be continuously energized and havecomplete control of the crossing signals.

The auxiliary track circuit apparatus is shown arranged to provide forcontrol of the crossing signals on movement of trains in the reverse aswell as in the normal direction of traflic. If control of the crossingsignals on movement of trains in the reverse direction is not required,the tube BGT and associated apparatus such as transformers BTT and BGT,and relays BTR and W, may be omitted, and the auxiliary track circuitapparatus may be employed to detect occupancy only of the portion of thetrack section between insulated joints 20 and I5.

In the system shown in Fig. 1 the alternating current employed in theauxiliary track circuit apparatus is supplied from a commercial sourceof current. If such a source is not available the alternating currentmay be supplied by a tuned alternator, and Fig. 2 illustrates such anarrangement.

Referring to Fig. 2 there is shown therein a tuned alternator TA whichmay be of any well known construction and which when supplied withdirect current supplies alternating current of a, suitable frequency,such as 60 or 100 cycles a second, to the transformer ST. The supply ofdirect current to the alternator TA is controlled by back contact 35 ofrelay CR so that the alternator is deenergized as long as the tracksection is vacant and is energized and causes alternating current to besupplied to the auxiliary track circuit apparatus as long as the sectionis occupied.

In the systems shown in Figs, 1 and 2 alternating current of the samefrequency is supplied over the track rails to the grid transformers asis supplied to the tube anode circuits. If desired energy of differentfrequencies may be employed for these purposes, and Fig. 3 shows such amodification.

As shown in Fig. 3 energy is supplied from the transformer ST to thetransformer T through a rectifier RX with the result that the frequencyof the energy supplied from transformer T to the track rails is twicethat supplied from transformer ST to the transformers ATT and BTT.

Accordingly, because of the higher frequency of the energy supplied tothe tube grids, there will always be a time during each half cycle inwhich energy of positive polarity is supplied to the anode of a tubethat the potential on the tube grid is such as to render the tubeconducting. This will be true even though there is a considerable phaseshift in the energy supplied over the track rails relative to the energysupplied to the tube anode circuits. The tube characteristics are suchthat once a tube becomes conducting it continues to be'conductingregardless of changes in the grid potential as lon as energy of properpotential and polarity is supplied to the tube anode circuit, so the useof the higher frequency energy in the track circuits will notsubstantially reduce the time during which a tube is conducting, and therelay which is energized by current supplied through the tube will besupplied with energy an adequate proportion of the time to keep itscontacts picked up.

The impedance of the reactor Is to flow of alternating currenttherethrough is proportional to the frequency of the alternatingcurrent, and if alternating current of relatively high frequency, suchas is made possible by the use of the frequency doubling arrangementshown in Fig. 3, is employed in the track circuits, the reactor I 6 maybe proportioned so as to have little resistance to the coded directcurrent track while having high impedance to the alternating currenttrack circuit energy so that a train on one side of the joint l willhave little shunting effect with respect to alternating current suppliedto the portion of the track section at the other side of the joint [5.This will insure prompt termination of operation of the crossing signalswhen a train passes beyond the joint 15, while it also permits the codeddirect current track circuit energy to be readily supplied through thereactor so that the maximum length of track section over which paratusmay be operated will not be substantially affected.

the coded track circuit ap- In the modifications shown in Figs. 1, 2 and3, the transformer T is provided with two secondary windings one ofwhich supplies energy to the portion of the track stretch at one side ofthe joint l5 and the other of which supplies energy to the'portion ofthe track stretch at the other side of the joint I5. If desired energymay be supplied from the same secondary winding to the portions of thetrack stretch. on both sides of the joint l5, and Fig, 4 shows such anarrangement.

Referring to Fig. hone end terminal of the secondary winding oftransformer T is connected to track rail l, while the other end terminalof this winding is connected through resistance 18 to the portion ofrail 2 at the left of joint l5 and through resistance 19 to the portionof rail 2 at the right of joint l5. When a train is in the portion ofthe track stretch at either side of the joint 15, the supply ofalternating current to the grid transformer on that side of theintersection is cut oil, while the resistor included in the circuit forsupplying energy from the transformer T to the track rails limits thecurrent taken from the transformer and thus prevents excessive reductionin the value of the energy supplied from the transformer to the portionof the track section at the other side of the joint l5.

When train is in the portion of the track section at one side of thejoint I5 it exerts a shunting effect through resistors l8 and 19 on theportion of the section at the other side of the joint. The resistance ofresistors l8 and I9 is so high, however, that the shunting effectexerted through them will not interfere with operation of the apparatuson the side of the joint opposite from the train.

In the modifications described above the secondary winding of thetransformer T is connected across the section rails and a reactor isconnected around the insulated joint l5 at the highway intersection topermit flow of direct current track circuit energy around the joint l5while preventing flow of alternating current auxiliary track circuitenergy between the portions of the track section on opposite sides ofthe joint I5 to thereby insure prompt cessation of operation of thecrossing signals when the rear of a train passes over the insulatedjoint It.

The need for the reactor can be eliminated by connecting the secondarywinding of transformer T around the joint [5 as shown in Fig. 4A. Inthis modification the transformer T is proportioned so that itssecondary winding has little resistance to flow of direct current, whilea current limiting resistance 56 is connected in series with the primarywinding of the transformer T to limit the energy supplied through thetransformer T to the track rails.

The grid transformers AGT and BGT are shown connected in series with thetrack rail 2, but they may be connected across the rails l and 2 asshown, in Fig. 9. A reactor 61 may be connected in series with the trackrelay 5TB to prevent flow of alternating current energy in the windingthereof, while an impedance of appropriate form, such'as a resistance68, is connected across the section rails intermediate the insulatedjoint 28 and the entrance end of the section to permit flow ofalternating current between the track rails while substantiallypreventing flow of direct current between the section rails.

The supply of energy to the transformer ST may be governed by a relay CRas shown in Fig. 1,

15 so that energy is supplied to the transformer when and only when theassociated track section is occupied.

When a train enters section 5T so that energy is supplied to thetransformer ST, energy is supplied therefrom through the resistance 65to the transformer T, while energy is supplied from the transformer T tothe grid transformers AGT and BGT over the circuit which is traced fromthe left-hand terminal of the secondary winding of transformer T overrail 2, through the primary winding of transformer AGT, through wheelsand axles of the vehicles forming the train to rail I; over contact itof relay CTM to rail 2, and thence through the primary winding oftransformer BGT to the right-hand terminal of the secondary winding oftransformer T. Accordingly, each of the grid transformers suppliesenergy to the associated tube so that the auxiliary track circuitapparatus operates as explained in connection with Fig. 1 to preventoperation of the crossin signals.

When the train advances beyond joint 2!), the shunt between the trackrails provided by the train prevents flow of energy from transformer Tthrough the primary winding of transformer AGT so the tube associatedwith transformer AGT ceases to be conducting and operation of thecrossing signals is initiated. At this time energy from transformer Tcontinues to be supplied through the primary winding of transformer BGT,but when the train advances beyond the joint I 5 the supply of energy totransformer BGT is cut off and the relay associated with thistransformer releases.

As soon as the rear of the train advances beyond the joint 55 energyfrom transformer T is supplied to transformer AGT over the circuit whichis traced from the left-hand terminal of the secondary winding oftransformer T over track rail 2, through primary winding of transformerAGT and resistor 68 to rail I, and thence through the wheels and axlesof the vehicles of the train to rail 2 and the right-hand terminal ofthe winding of transformer T. Accordingly, the tube associated withtransformer T is rendered conducting and operation of the crossingsignals is discontinued promptly when the rear of the train clears theintersection.

When the rear of the train passes over joint 22 energy from transformerT is again supplied to transformer BGT and the relay associated withthis transformer picks up. When the train vacates the track sectioncoded direct current supplied at the exit end of the section feeds tothe track relay 5TB and operates it so that the supply of energy totransformer ST is cut off and the auxiliary track circuit apparatusceases to function.

The equipment operates in a similar manner on movement of a trainthrough the track stretch in the reverse direction.

In the modifications shown in Figs. 1 to 4 the coded direct currenttrack circuit nergy must be supplied through the reactor It. Thisreactor will have some resistance to the coded direct current and willtherefore reduce the maximum perable length of track circuit. This canbe overcome by substituting for the reactor a circuit controlled by theauxiliary track circuit apparatus and shunting the joint l5, and Fig. 5shows such an arrangement.

Referring to Fig. 5, a circuit shunting the joint 15 is established whenthe contacts of relays E and W are picked up. This circuit includesfront contact 10 of relay E and front contact 1| of relay W. Theequipment is otherwise the same as that shown in Fig, 1 except that thereactor i6 is omitted, while a transformer with a single secondarywinding, as shown in Fig. 4, is employed to supply energy to the sectionrails. This type of transformer is necessary to prevent short circuitingof the transformer secondary by the shunt circuit which is at timesestablished around the joint [5.

When the track stretch is vacant relays E and W are held picked up byenergy supplied over front contacts of relay CR so contacts 70 and Hestablish the circuit shunting the joint l5 and coded track circuitenergy may flow around joint !5 through the shunt circuit. Theresistance of the shunt circuit may be extremely low so that there islittle impedance to the flow of coded direct current track circuitenergy over the section rails.

When a train enters the track section relay CR. releases and establishesthe circuit to supply energy to transformer ST so that the auxiliarytrack circuit apparatus functions as explained in connection with Fig. 1to supply energy to relays E and W and keep them picked up although thecircuits controlled by relay CR for supplying energy to these relays areinterrupted.

When the train enters the approach section at the left of joint l5 relayE releases and its contact 50 interrupts the circuit of winding of theinterlocking relay XR to thereby initiate operation of the crossingsignals, while contact 70 of relay E interrupts the shunt circuit aroundjoint I 5. Since the section is occupied at this time there is no needfor the coded direct current to be supplied around joint [5 andinterruption of the shunt circuit will not interfere with operation ofthe traffic governing signal system.

When the train advances beyond joint (5 relay W releases and its contact1| additionally interrupts the shunt circuit around the joint [5.Accordingly, when the rear of the train passes beyond the joint l5 thetrain ceases to exert any shunting effect on the alternating currentsupplied to the portion of the track section at the left of joint [5,and the auxiliary track circuit apparatus associated with the portion ofthe track section at the left of joint l5 will function immediatelyafter the rear of the train passes over joint [5, and relay E will pickup to discontinue operation of the crossing signals.

When the train advances farther in the track stretch relay W will bepicked up, as explained in connection with Fig. 1, while on picking upof relay W its contact ll completes the circuit shunting the joint l5.At this time, however, the train is so far removed from the joint l5 asto have little or no effect on energy supplied from transformer T to thesection rails, and the relays E and W are maintained energized by theauxiliary track circuit apparatus.

When the train advances far enough to vacate the section 5T, codeddirect current supplied to the track rails at the exit end of thesection feeds over the track rails and through the shunt circuitestablished by front contacts 70 and H of relays E and W to the trackrelay and operates it so that the relay 5H is picked up and establishesthe circuit of relay CR, Accordingly, the relay CR picks up and itscontact cuts off the supply of energy to transformer ST and thusdiscontinues operation of the auxiliary track circuit apparatus, whilecontacts 2'! and 28 of relay CR establish circuits for the relays W andE so that their con- 17 tacts are maintained'picked up to maintain theshunt circuit around the joint l and to prevent operation of thecrossing signals.

The modification shown in Fig. 5, like that shown in Fig. l, operates sothat if on entrance of a train into the track section, one of theelectron tubes is defective, or the auxiliary track circuit apparatusdoes not function for any other reason, operation of the crossingsignals will be initiated as soon as the train enters the sectioninstead of being deferred until the train advances to a predeterminedpoint in the section. In addition, the equipment shown in Fig. 5operates so that operation of the crossing signals will not bediscontinued when the train passes the intersection if the auxiliarytrack circuit apparatus is not functioning properly.

When the equipment is arranged as shown in Fig. 5, if the auxiliarytrack circuit apparatus is defective, the circuit shunting the insulatedjoint i5 will not be established when the approach sections on oppositesides of the highway crossing are Vacated. Accordingly, when the trainvacates the track section, coded direct current energy supplied at theexit end of the section cannot feed to the track relay, and theassociated relay 5H will remain released and will not establish'thecircuit of relay CR. As a result the relay E or W will remain released,the one depending on which part of the auxiliary track circuit apparatusis defective, and the crossing signals will continue to operate, whilethe signal at the entrance to section 5T will display its stopindication and energy of 7 5 code frequency will be supplied to therails of the adjacent section in the rear to cause the signal for thatsection to display its caution indication.

The continued operation of the crossing signals and the continueddisplay of a stop indication by the signal at the entrance to section 5Twill provide an indication that the equipment is not functioningproperly.

The failure of the equipment shown in Fig. 5 to resume normal operationwhen the section is vacated if the auxiliary track circuit apparatus isnot functioning properly may be overcome by employing means toperiodically establish a circuit shunting the joint I5, as shown in Fig.6.

Referring to Fig. 6, a coding device 200T is provided which has acontact 13 which when closed establishes a circuit shunting the joint15. The contact 13 of the coder ZIJCT may be operated at any appropriaterate, such as 20 code frequency, which is substantially different thanthe rate of operation of the coders controlling the supply of trafficgoverning energy to the section rails. The coder 290T may operatecontinuously, or it may be controlled as shown by contact 12 of relay CRso as to operate only when the section is occupied. 7

With the arrangement shown in Fig. 6 when a train passes through thesection and the auxiliary track circuit apparatus is functioningproperly, the relays E and W will be picked up and establish the shuntcircuit around joint I5 when the section is vacated, as explained inconnection with Fig. 5. If when the section is vacated one of the relaysE or W remains released, the shunt circuit controlled by these relayswill not be established, but contact 13 of coder ZBCT will periodicallyestablish a circuit shunting the joint 15. During the closed periods ofcontact 53 coded track circuit energy supplied at the exit end of thesection will feed around the joint l5 over the circuit established bycontact 13 to the track relay and operthrough the tube over the ate itso that the associated code detecting relay 5H picks up to establish acircuit for relay CR. When CR picks up it establishes circuits forrelays E and W and they pick up to discontinue operation of the crossingsignals, and to establish the circuit which they control for shuntingthe joint l5.

With the arrangement shown in Fig. 6, when a train is in section 5T withthe end of the train adjacent one side of the joint l5, during the.

closed periods of contact 13 of coder 200T the train will exert shuntingefiect on the auxiliary track circuit energy supplied to the portion ofthe track section on the opposite side of the joint 15. The relays E andW may be of a type which are slow enough in releasing to remain pickedup during the periods in which contact 13 is closed, and thus preventmomentary operation of the crossing signals.

In the modifications shown in Fig. 1 a relay ATR is energized throughthe tube AT and controls the supply of energy to a winding of relay E.It is possible, however, to energize the winding of relay E from thetube AT, and thus eliminate the relay ATR, and Fig. '7 illustrates sucha modification.

The modification shown in Fig. 'l is the same as that shown in Fig. 1except that the relay ATR and the transformer ATT have been eliminatedand the anode circuit of tube AT has been connected to a winding ofrelay E, while the grid biasing resistor 44 is connected between theline wires 92 and S3. The condenser 55, employed in the system shown inFig. 1, is connected across the terminals of the winding of relay E.

As long as the section is vacant relay E is held picked up by energysupplied over contact 28 of relay CR as explained in connection withFig. 1. When a train enters the section relay CR releases and causesenergy to be supplied to transformer ST so that energy is supplied overthe track to transformer AGT to render the tube AT conducting, whileenergy is also supplied to the tube anode circuit. Accordingly, energyis supplied line wires 92 and 93 to a winding of relay E and serves tokeep the contacts of relay E picked up. i

The various parts of the equipment are arranged so that the energysupplied to the relay E through the tube AT is of the same relativepolarity as the energy supplied to the relay E over the circuitcontrolled by contact 28 of relay CR so that the contacts of relay Ewill remain picked up on transfer of control of the relay from theprincipal to the auxiliary track circuit apparatus.

When a train enters the portion of the track section between insulatedjoints l5 and 20, energy is no longer supplied to transformer AGT andthe tube AT ceases to be conducting and energy is no longer supplied torelay E and its contact releases to initiate operation of the crossingsignals.

When the portion of the track section between insulated joints l5 and 20is vacated, energy is again supplied to transformer AGT so that the tubeAT is rendered conducting and energy from the transformer ATT issupplied through the tube AT to a winding of relay E to pick up itscontact and discontinue operation of the crossing signals. When thetrack section is vacated relay GR is picked up and discontinuesoperation of the auxiliary track circuit apparatus and establishes acircuit to energize relay E.

The modification shown in Fig. 8 is similar to that shown in Fig. 7. Inthe sytem shown in Fig. 8 the transformer ATT isnot employed and thesecondary winding of transformer ST is connected across the anode andcathode of tube AT through a current limiting resistor Q and over linewires 95 and 93, while the grid biasing resistor 3 3 is connectedbetween wires 56 and 98. A winding of relay E is connected across wires95 and 98 on the side of resistor 95 remote from the transformer ST.

When relay CR is released so that energy is supplied to transformer ST,energy is supplied through transformer T to the track rails, and thus totransformer AGT to render the tube conductme. In addition, when energyis supplied to transformer ST, energy will be supplied from thetransformer secondary winding through the resistor S5 to line wires 95and 93, and therefrom to the winding of relay E.

During the half cycles in which the impulses of energy induced in thesecondary winding of transformer ST are such that energy of positivepolarity is supplied to wire 98, energy will be supplied through thetube AT, assuming that it is conducting, so that the transformersecondary is in effect short circuited through the tube, and the tubeserves to divert energy from the winding of relay E. The resistor 95serves to limit the supply of energy from the transformer ST and thusprevents overloading of the tube AT.

During the half cycles in which the impulses of energy induced in thesecondary winding of transformer ST are such that energy of positivepolarity is supplied to line wire 98, energy will not be suppliedthrough the tube AT, and all of the energy supplied through resistor 95will be supplied to the winding of relay E.

Accordingly, when the tube AT is conducting, the impulses of energy ofone polarity supplied to the winding of relay E are of substantiallylower value than those of the other polarity, and as a result there is asubstantial direct current component in the energy supplied to thewinding of relay E and is eifective to maintain the contacts of therelay E picked up.

The various parts of the equipment are arranged so that the directcurrent component of the energy supplied from transformer ST to awinding of relay E is of the same relative polarity as the energysupplied to relay E over the circuit controlled by relay CR. Thisinsures that the contacts of relay E will remain picked up when controlof relay E is transferred from relay CR to the auxiliary track circuitapparatus.

When the portion of the track section between the insulated joints 20and i5 is occupied energy is not supplied to transformer AGT and thetube AT ceases to be conducting. Under these conditions impulses ofenergy of the same value are supplied to the winding of relay E duringboth halves of the cycles of energy induced in the secondary winding oftransformer ST. Accordingly, there is no direct current component in theenergy supplied to the winding of relay E at this time and the contactsof the relay release and initiate operation of the crossing signals,while the winding of the relay may have high inductance to reduce theflow of alternating current therein.

When the portion of the track section between the joints l5 and 20 isvacated and the tube AT is again rendered conducting, the direct currentcomponent is again present in the energy supplied from transformer ST tothe winding of relay E and its contact is picked up to discontinueoperation of the crossing signals.

When the track section is vacated relay CR 20 is picked up and itscontact 35 interrupts the circuit of transformer ST to thereby preventoperation of the auxiliary track circuit apparatus, while relay E ismaintained picked up by energy supplied over front contact 23 of relayGB.

The modifications shown in Figs. 7 and 8 have been illustrated anddescribed in connection with the circuits associated with the tube AT,but it is to be understood that these modifications are 1() equallyapplicable to the circuits associated with the tube BT.

In the modifications already described the primary windings of the gridtransformers AGT and BGT have been connected in series with the trackrail so that coded direct current track circuit energy must be suppliedthrough those windings.

While the transformers AGT and BGT may be provided with primary windingshaving low resistance to the coded direct current track circuit energy,these windings will have some resistance to such energy, and will reducesomewhat the maximum length of track section over which the coded trackcircuit can be operated. The series connection of the grid transformersis not essential, and these transformers may be connected across therails as shown in Fig. 9.

Referring to Fig. 9 the transformer AGT has one terminal of its primarywinding connected to one track rail and has the other terminal of itsprimary winding connected to the other track rail through a resistor I80which serves to limit flow of coded direct current track circuit energyth ough the transformer primary winding.

The transformer AGT is located at a point in the track stretch farenough in the rear of the highway crossing so that if operation of thecrossing signals is initiated When a train advances beyond thetransformer, the crossing signals will be operated for at least apredeter- 4 mined interval before the train reaches the intersection.

The equipment at the intersection as well as the equipment associatedwith transformer AGT may be arranged as shown in any of themodifications previously described.

In operation, when a train enters the section so that alternatingcurrent is supplied to the section rail at the intersection, this energyis supplied to the primar winding of transformer AGT with the resultthat energy is supplied from the transformer secondary winding to thegrid of the associated tube to render it conducting and thus preventoperation of the crossing signals.

When the train advances beyond the transformer AGT the supply ofalternating current to the transformer is cut off and the tubeassociated with transformer AGT ceases to be conducting and operation ofthe crossing signals is initiated and is continued until the trainvacates the portion of the track section between transformer AGT and theintersection.

In addition, when a train is present in the track section and isapproaching the transformer AGT, it shunts alternating current from thetransformer and thus reduces the value of the energy supplied from thetransformer AGT to the grid of the associated tube. The shunting effectof the train on the transformer AGT gradually increases as the trainapproaches the transformer and before th train reaches the transformer,

may cause the energy supplied to the grid of the associated tube to bereduced to a value ineffective to maintain conductivity of the tube. Asa result operation of the crossing signals will be initiated before thetrain reaches the transformer, and the signals will be operated forsomewhat longer than the minimum period prior to arrival of the train atthe intersection. The shunting effect of the train on the transformerAGT will vary somewhat with ballast conditions, so the point to whichthe train must advance before operation of the crossing signals isinitiated will vary with changes in ballast conditions. However, asoperation of the crossing signals is always initiated when the trainadvances beyond the transformer AGT, and as this provides for theminimum period of operation of the signals, the system is entirely safeand any variation in the period of operation of the signals is in excessof the minimum period.

If preferred as shown in Fig. 9A a condenser NH ma be substituted forthe resistor 15% in the circuit of the primary winding of thetransformer AGT. The condenser iii! operates to permit alternatingcurrent auxiliary track circuit energy to be supplied to the transformerAGT, while preventing flow of the coded direct current signal controlenergy to this transformer.

The transformer AGT may be inductively coupled with the track rails. Asshown in Fig. 10 a loop I82 consisting of a plurality of turns of wireis mounted between the track rails with portions of the loop adjacentthe rails l and 2. The ends of the loop are connected to the terminalsof the primary winding of the transformer AGT.

When alternating current is supplied to rails l and 2 at theintersection, and the portion of the track section between the loop andthe intersection is vacant, alternating current flows in the portion ofthe rails I and 2 adjacent the loop I02 and induces energy in the loopfrom which it is supplied to the primary winding of transformer AGT, sothat energy is supplied from the secondary winding of transformer AGT tothe grid of the associated tube and causes the tube to be conducting.

When the portion of the track section between the loop and theintersection is occupied, alternating current no longer flows in theportion of the rails l and 2 adjacent the loop N32, and energy is nolonger supplied from the loop through transformer AG I to the tube gridand the tube becomes non-conducting.

The modification shown in Fig. 10, like that shown in Fig. 1, operatesso that the crossing signals are not started until the train advancesbeyond a predetermined point in the track section.

The modification shown in Fig. 10 results in no impedance whatever tothe supply of coded direct current energy over the track rails andconsequently does not affect the length of track circuit which can beoperated.

This crossing signal control system is adapted for use where there aretwo highway crossings relatively close together so that the approachsections for the crossing signals overlap, while the system is alsoadapted for use where a crossing is adjacent an end of a track sectionso that an approach section for the signal for that crossing extendsinto the adjacent track section, and Fig. 11 is a diagram illustratingthese modifications.

Fig. 11 consists of Figs. 11A and 1113 which when placed together withFig. 113 at the right, is a diagram of a stretch of railway track overwhich traific normally moves in the direction indicated by the arrow,that is from left to right. The rails l and 2 of the track stretch aredivided by insulated joints 3 into track sections for signalingpurposes. and are designated IT and BT,

Each track section has at the entrance end thereof a wayside signal,designated S with an appropriate prefix, while each track section isprovided with coded track circuit apparatus for controlling the signalfor the section, and for also controlling the supply of coded energy tothe rails of the adjacent section in the rear. The coded track circuitapparatus employed in sections IT and ST is similar to that employed inthe system shown in Fig. l and a detailed description of the trackcircuit apparatus is unnecessary.

The track circuit apparatus for section IT includes coded feed-backequipment for indicating at the exit end of the section whether or notthe section is occupied. The coded feed-back equipment may be arrangedin any manner well known in the art, and has been shown arranged asshown in Letters Patent of the United States No. 2,286,002 to Frank H.Nicholson.

The track stretch includes intersections with highways HI and H2. Theintersection with highway H! is located in section 1T, while theintersection with highway H2 is located in section 8T at a pointadjacent the entrance end of the section so that on movement of a trainin the normal direction through the track stretch it is necessary tostart operation of the crossing signals KS2 for the intersection H2before the train enters section 8T.

The crossings HI and H2 are located so close together that the approachsections for the signals for the two crossings overlap. It is necessaryon movement of a train in the norma1 direction through the track stretchto, initiate operation of the crossing signals X82 before the trainadvances to the point in the track stretch at which it is necessary toinitiate operation of the crossing signals XSI on movement of a trainthrough the track stretch in the reverse direction.

Alternating current of one frequency, such as 60 cycles per second, isemployed in the auxiliary track circuit apparatus for the control of thecrossing signals X88, and alternating current of a different frequency,such as cycles per second, is employed in the auxiliary track circuitapparatus for the control of the crossing signals X82, while filters ofwell known design are provided at appropriate points to preventinterference between the two sets of auxiliary track circuit apparatus.

The construction of the filters is not a part of this invention, and tosimplify the disclosure these have been shown diagrammatically in thedrawings.

The same reference characters are employed in Fig. 11 to identify thevarious elements of the auxiliary track circuit apparatus as areemployed in Fig. 1, while in Fig. 11 the reference characters for theauxiliary track circuit apparatus for the control of signals XS! arepreceded by the prefix I, and those for the apparatus for signals X82are preceded by the prefix 2.

The equipment is shown in the condition which it assumes when the trackstretch is vacant. At this time energy of code frequency is supplied tocoding relay BCTM so that it supplies energy of this code frequency tothe rails of section BT and this energy feeds to track relay 8TB andoperates it with the result that energy is supplied through the decodingtransformer flDT to relays 8H and BJ. As relays 8H and SJ are both 75picked up signal 88 displays its green or clear Two track sections areshown,

